MP 1,1-5,1 Troubles with Mac Pro 4,1 dual CPU board SMC

[philippe_elie]

Hi all,

I just acquired a dual CPU board for my Mac Pro 4,1 with the intention to later replace the installed 2.26G Xeon chips with X5690s and swap my original single 2.66Ghz CPU board. I had already upgraded the firmware to 5,1 , migrated to Mojave, both SMC (main board and CPU tray) are at 1.39f5, both boards are 4,1 then so all fine from that side.

My issue is a fairly common one : all fans full speed, AHT reports " 4SMC/1/40000000: SMC", but both CPUs work fine and Mac Fan Control allows to control the fans and make the MP usable. Obviously I attempted to reset the SMC but that did not make any difference

I could not identify the root cause despite lots of Google searching and several attempts to fix the sensors, namely :
- Macs Fan Control does not report any sensor related to CPU A. Interestingly, no DIMM proximity information for CPU A as well, as if all the CPU A side was simply ignored. All CPU B sensors (core, heatsink, DIMM proximity) appeared OK.
- I tested the CPU A heatsink sensor (a 2N3904 transistor), characteristics looked fine but I replaced it anyway with the same reference. I proactively replaced the the Northbridge heatsink. No change.
- I also removed CPU A (necessary to remove the CPU tray metal frame and get access to the Northbridge heatsink rivets) but I did not change the sensor as it reported OK.
- I took the opportunity that the 2 CPU and Northbridge heatsinks were removed to clean the thermal paste and replace it

Net result is :
- no change regarding fans : still all full speed and AHT reports the same error
- now CPU B core sensor does not appear any longer, only CPU B Heatsink is reported by Macs Fan Control.

I'm afraid I am running out of answers... Do you think I should replace the CPU A heatsink sensor - the only remaining one I did not replace at this stage ? Should I try swapping the CPUs to figure out if that makes any difference ?

Thanks in advance for any input you may provide

Philippe

 

[philippe_elie]

FYI I just swapped the CPU : no change. Only CPU B heat sink, CPU B DIMM proximity and IOH (Northbridge) heat sink and diode are reported.. and still nothing CPU A-related. looks like the board has a problem. I sprayed some F2 contact cleaner on the CPU A contact with no effect.
I think I will have to live with Macs Fan Control... but not understanding where this comes from really worries me.

 

[h9826790]

If you just get that tray, may be it's faulty from the very beginning.

 

[philippe_elie]

Yes I just bought it from eBay, seller clearly stated that there was a fan problem but that both CPU run fine. I ordered it anyway for approx 250USD for it, which I think is ok considering I can use Macs fan control append and that i assumed i could fix the sensor issue.

 

[jasonmacpro31]

Sounds like the SMC is bad

And probably needs replacing even if you can figure out which chip it is :-/

 

[philippe_elie]

Sounds like the SMC is bad

And probably needs replacing even if you can figure out which chip it is :-/

Hi Jason,
So far I live with Macs Fan Control and it works just fine. CPUA heat sensors - heatsink and core - as well as DIMMs 1-4 are not detected so I have to live with CPUB and Westbridge sensors but so far so good. I had to tweak things quite a bit to migrate to Mojave. Also have boot camp running with W10 pro so both CPUs are detected. It’s amazing how this machine who is now 10 years old is amazingly powerful.

 

[jasonmacpro31]

I would say I have a similar issue

But I can’t get my CPU B to detect a CPU lol


But the board don’t see the ram slots or cpu temp’s from slot B with no CPU in there so it seems although the fan is running perfectly

 

[philippe_elie]

I would say I have a similar issue

But I can’t get my CPU B to detect a CPU lol


But the board don’t see the ram slots or cpu temp’s from slot B with no CPU in there so it seems although the fan is running perfectly

I had to delid the CPUs and clean the contacts very carefully. The CPU boards sockets are very fragile and I used a magnifying lens to check the pins, they are super sensitive. You have to apply pressure when securing the heatsinks very evenly.